Cyclic process for production of anhydrides of carboxylic acids



Patented Oct. 28, 1941 CYCLIC PROCESS FOR PRdDUOTION AN HYDRIDES OF CARBOXYLIO ACIDS Aylmer H. Maude and assignors to Hooker Elec- Niagara Falls, N. Y.,

trochemical Company,

poration of New York Sidney 1G. Osborne,

New York, N. Y., a cor- No. nmvmg. .Application mne'so, 1939,

Serial No. 282,148

13 Claims. (Cl. 260-548) 5 The production of anhydrides from carboxylic acids involves extraction of a molecule of water from two of the acid which must of course be anhydrous. Anhydrous carboxylic acids, whether produced by synthesis or by dehydration of the aqueous natural'acid, are expensive. dride has hitherto, in general, been produced either from the. acid, by pyrolysis, with much expenditure of heat energy, or from its salts, with much Waste of reagents. The object of our inven-, tion is to provide a process which shall be of wider applicability and more economically sound than any hitherto known. In the pursuance of this objective, we start with the dilute natural or synthetic acid, avoid pyrolysis and eliminate waste by recycling all the principal by-products.

' At present the most important of the anhydrides is perhaps that of acetic acid,as cellulose acetate is producedby reaction of cellulose with acetic anhydride. In this reaction water is extracted from the cellulose. This combines with acetic anhydride, converting it to acetic acid.

Inthe washing of the product, this acetic acid becomes greatly diluted. It is an economic necessity that this dilute acetic acid be recycled in theprocess. For this purpose it must of course at some stage be freed from the water. The concentration of acetic acid is diflicult andexpensive. Itis one of the objects oi our invention to provide a practicable process by which'acetic anhydride can be economically produced from the dilute acetic acid of the cellulose acetate process without the. necessity for first concentrating it, by making up a stable salt from the diluteacid and thendehydrating the salt.

Acetic anhydride may be produced from acet lene, by synthesis, or from acetic acid, either directly, as bypyrolysis, or through its salts,,by various reactions. In thelatter case, the acetate may be reacted with sulphur chloride, sulphur trioxide, a chlorsulphonate or a pyrosulphate (the two latter of which reagents may be regarded as carriers ofSOa).

The process which produces acetic anhydride from acetylene is of course inapplicable to the recycling'of acetic acid recovered from the cellulose acetate process. "The pyrolytic process for making acetic anhydride directly from acetic acid, if used in connection with the cellulose acetate process-involves first'concentrating the dilute acid of that process, which it is one of the objects of our invention to avoid: The pyrolytic process is also technically diff cult, involves a high initial investment and is extravagant of heat energy. c

'Theproc'esses in which an acetate is reacted with sulphur chloride, sulphur 'trioxide, a chlorsulph'onate or a pyrosulphate, as at present operatedfor proposed, are extravagant of reagents,

The anhy-,

as-they result in large production of waste bysulphur and chlorine, which may have been purchased in the form oisodium chloride, sodium carbonate, elemental sulphur, sulphuric acid, sulphur chloride or elemental chlorine and there-.

fore represent substantial values.

.In Dreyfus Patents Nos. 1,283,land 1,338,979 there is disclosed a processior reacting anacetate withsulphur trioxide. however, be carried out at ordinary temperatures because under such conditions the sulphur tri oxide decomposes the acetic anhydride produced.

The reaction must, therefore be carriedv out, ac,- cording to the patents, below 5 C. As a matter of fact, it is preferably carried out at -40 C. This is below the. freezing point of S03, which must thereforebe usedin gaseous form, .diluted withair. The aircarries ofi some of the product.

On this account and because of secondary .reactions, the yield is never better than 80 percent.

Moreover the sulphate and chloride formed are be dehydrated waste products. I v I .InDreyfus Patents Nos. 1,283,115 and 1,368,789 there is disclosed a process for reacting dry sodium or calcium; acetatewith sodium chlor: sulphonate to produce acetic anhydride, sodium or calcium sulphate and sodium chloride, the latter of which are waste products. The calcium acetate reaction of the disclosure should, how-.

ever, be dis'regarded'as calcium acetate cannot by ordinary methods without decomposition to calcium carbonate and acetone. In. the alternative reaction the sodium sulphate and'chloride formed as the by-products are both water soluble. Their separation is consequently difhcult. That this is an important objection will .be shown later.

'Our process is of the general typeof that in which. an acetate is reacted with a chlorsul-' phonate, but difiers'irom the prior art in that, for reasons that will hereinafter appear, we prefer to use an acetate which has not been hitherto proposed for this reaction, e. g., barium acetate.

This acetate is more readily dehydratable than the sodium acetate of. the prior art. Thus,

sodium acetate requires to be dehydrated under vacuum at 0. Since it fuses "at this temperature, this process involvesstirring a viscous, plasticmass and consumes'muchpower. Barium acetate, on the other hand can be dehydrated in granular form in a retort dryer at any temperature between 42 and 200 C'., without vacuum. Moreovenbarium sulphate is highly insoluble, therefore easily separated from sodium chloride. It is also readily convertible .to barium. sulphide or oxide, which readily react with dilute acetic acid. As will be shown later, this combination I of properties, lends itself to'the development of products, carrying. out of .the process sodium,

This reaction cannot,

1 drous.

peratures, it is impractical to carry out this ;reac+ I tions, or there may be anexces's of chlorsulpho ,acetic 'anl ydridais the nly, medium used, the 4 ti on. l.finy"acetate remaining in the residue may of Equation 1 is reconvertedto' barium acetate according tothe following equations: v p

BaSO4+2C-|-heat=BaS+2CO2 (2) Ba(CH3CO2)2+NaSO3Cl=(CHsCO)2O+ 3 3 BaSO4+NaCl (1') I iThe HzS of Equation 3 is then oxidized to S03- and H20 in accordancewith the following, equations: 7

H2S+3O=SO2+H2O (4) "SQ2+O=SOs (5) a cyclic process-which is one ofthe; objects of our invention 'fl Our principal reaction is therefore as follows:

'In this reaction, as in those of the-prior art, the acetate must, for obvious'reasonabeanhp The chlorsulphonate r ou segneees-' sarily so. l I

As both reagents are solid atprdinary tem:

which,fbeing exothermic, they are self-sustaining. Enough oxygen is used to completely oxidize the H28 to S0 with a slight excess. The $02 of Equation 4 is of course wetand must be dehydrated. The oxygen fused 'inEquation? 5 must likewise be anhydrousi This results in; pro-:

tion without theuse of a liquid .medium."'-The preferred medium would of' course be'asolvent. and one which did not afterward have to be remoedfrom the product. Fortunately, barium a ate' 'is'j slightly "soluble in glacial acetic acid. he product is to be used in the cellulose me 7 acid is"not objectionable or uneconomical since the reaction of that proces s 'involve s "the aci'd'as 7 Well vas, the anhydride i Heh'efbrthis and ether The NaCl solution" is then evaporated to dryness. reas ons' to begiverrlatenf-our process {is' prefer- B O Equation 5 e (Nacl 0f q fiablyistarted by making up-a paste of the reagents tion' -1 are then 1 reacted together to form b m gn of glacial: acetic amid t- Na'SQaCl in accordance with the following equa.-:

The NaCl' of Equation 1 is separated from'zthe 32304 by simply dissolving it out as with Water;

sary that the reagents, be completely in-solution ti'on': 7 at thestart of the reaction, as'thereagentsini 3+ flSQaCl (6) I a yin-s lut n ar 'consta t r p e i b3, .f The oxygen of Equations 4 and 5*is supplied fresh-reagents as the-reaction proceeds. again V a i As an alternative to Equations 2 and 3 the following reactions may be employed to acco m plish the same resultz-- a The reaction 'will also take place in the ab} sence' of glacial aceticacid if acetic anhydride be .pr esent,' as' of course itjis'assoon as the re-- actio'n has been initiated, [In this-case" the an-- ydride.: isubelieved to react with the chlorsul- 7 V I 4 phonate; forming intermediate p'roducts whioh i), ZCHLCQOH'PBQOT-BMCHBCOQ 2+H20 (8)1 eventually go over to the anhydride.'- e

The-reaction is exothermic arid starts'at-room temperature. Good mixing is essentiaLfThis Can be' accomplished by'using a reactor provided 40 Wi'i a stirrer o m e I I. I Thereagents may be in-equirmolecular propor- Itmay be considered that in these equations car-; bon has been used partly as fuel 'and'partlyas a reagent, but in Equation 7"a larger'proportion has been used as fuel. Although Equations 7 and 8"may appear simpler. than Equations 2 to .4,

nate'mfbanfum acetate. In the former case, '1 atu'res' i'nvolved are lower.

, course be'ordinaryxcommercial acetic acid onthe dilute acid of the cellulose acetate process above referred to. In that case thebarium acetate-of reactionfdoes not go to completion but ,aeetic radical and S03 acidity are foundin the residue; l f t here is a large excess Qf: chlorsulphonate, the reach will. 9 J c m l i n so awe p a e is @qncemed butl-a'cetylliqhlorideahdispe of Equat1on8, must obviously'be clehydratedsa As m p a forma n' hei. h -7.; already stated, this is easily effected, .asg-this salt gi a' aj g c acid i i-" n fi -m m 5 li istquite stable and. can'withstand. dehydrating e e y be I u b g temperature without decompos1t1on.. 4. The ba'rium acetate; of Equations. 3 orf8t and and the reaction, will go to 98per cent ofcom pletism in-about ou hours at o m mp at the sodium chlorsulphonate' of Equationtfi are of ordinarily without the necessity for h'ea'ting or i I cooling, For this' and oth'er reasonsalready given; the addition of glacial acetic acid at the star't o fthereaction is'our preferred practice."

course recycled'for the next batch.

5 e I r. 1,000 lbs. of 2-0 'per centfacetio acid were lieu:

tralized with 315 lbs.- of 90 per cent-barium .sul-

j Upon" completion of.;Reacti on"1 the acetic an-.- 1 H i I ydr d and a c a es l d h the p 1deand the so ution bo1led to expel all vHas.

I reaction products, under "vacuum; within atern The H s was passed to a contact sulphuric acid perati re, range finishing at"200?"C 'Ihelproduct u vuantit was made u to 133Tlbslb SO' 'd'riif'd is pr ierably. condensedi'by refrigeration. The q y 3 e from combustion of sulphur in the s'amecontact 'viproductf abut-@1115, 5 Per cent Sulphur; o5 sulphuric acid plant. The barium acetate s'olu tion was evaporated by boiling and theresidtial which maybe reduced jto a; trace by I fractiona i be covered t t nt t e h s tact sulphuric acid plant was absorbed in 107.15g. at 2 ...C-. a -;t c v t o or dry salt'in a rotary Water-cooled ractorli'lThe cour be dehydratedbefore. reuse, Theoverall 7 resulting sodium .chlorsu1phonat.. was. trans y d hq pr e s. s a ov'e'. 0ut1ined better ferred to a mixingmachine and therewas added than5 percent oi the theoretical yield to;.itthe dry bariumacetate and 323'jlbs; or; an: )ur process. also difiers{irorn thatof the prior hydrous acetic acid; Thematerials' were mixed art in that it includes steps subsequent to the for six. hours with cooling." From the resulting principal "reaction by which the barium sulphate mass'were distille'dofi 310'lbs. fo'f acetic'acid'and Reactions 4 and 5 are started by ignition. after duction of S03, which is. necessarily anhydrous, process, thefprese'ncef of glacial a t 20 as it cannot :exist as such in contactwith Water;

1 Equations 2 and 7 involve consumption of fuel; Y

- The acetic acid'of'Equation's 3 and 8 may Equation 3, and'in any case the barium acetate a plant and converted to 126 lbsl oi 'SOaand this acetatedriedat C. The soaifromthe' oh accuser 153 lbs. of acetic anhydride. This quantity of acetic 'anhydride represents a yield of 90 per cent of the theoretical quantity. The residue was leached with water to remove salt and the reinaining 430 lbs. of crude barium sulphate were reduced with '60 lbs. of anthracite coal in an electric tube furnace at a white heatto produce 332 lbs. of '85 per *centbar-ium sulphide.

Example II 1,000 lbs of '20 per cent acetic acid were "neutraliz ed with 255 lbs. crude barium oxide. The solution obtained was evaporated by boiling and the residual acetate dried at 160 C. The dry acetate was mixed for 'six hours while cooling with 323 lbs. "of anhydrous acetic acid and 235 lbs. sodium chlorsulphonate. From the resulting mixture was distilled off under vacuum 310 'lbs.'of acetic "acid and '153 lbs. of acetic anhydride. "The residue was leached to remove the sodium chloride and the remaining 430 lbs. of crude barium sulphate were dried and ignited in an 'electric'furnace to regenerate 250 lbs. of crude barium oxide and 140 lbs. of sulphur trioxide.

The sulphur trioxide evolved together with 'lbspsulphur trioxide from another source to make the inevitable losses were reacted withlOl lbs. of salt to regenerate the sodium chlorsulphonate used. This reaction was conducted in a watercooled mixing machine.

It will therefore be seen that the only waste products of our process are the CO2 of Equations '2 or '7 and the H20 Equations 4 or 8, which originally cost practically nothing and have no commercial value. The only raw materials to be supplied are therefore carbon and acetic acid. The acetic acid used in'Equations 3 and 8 need not be glacial but may be ordinary commercial or dilute acetic acid. Our process is therefore completely cyclic in respect of the barium, sulphur' and chlorine used, except for trifling losses in the 'f'o'rmof dust, etc.

While it would be theoretically possible to recycle the sodium sulphate of the prior art, to the best of our belief this has never been done or proposed; moreover, the economics of doing so would not be comparable with those of our process for the following reasons: sodium sulphate fuses at 884 C. and must be fused before it can be converted to the sulphide or oxide. This reaction is therefore one of considerable difficulty, requiring very special apparatus. Barium sulphate, on the other hand, can be very easily converted in commercial apparatus of wellknown type.

In our process as described we are therefore enabled to recycle our by-products because of our use of barium acetate in place of the sodium acetate of the prior art.

By the substitution of barium acetate for sodium acetate we have accomplished the following highly useful results:

(a) We have facilitated dehydration of the acetate.

(11) We have facilitated separation of the sulphate from the chloride.

(0) We have made practicable the re-cycling of the sulphate, and consequently of the chloride, reduced the waste products to water and a gas of negligible value (thereby eliminating the disposal problem) and limited to the raw materials to fuel and the essential chemical involved in the reaction, namely acetic acid.

dilute. 'While we havedescribed our "processes carried out with barium acetate, we do not wish to be limited thereto, as certainother meals,.such as zinc and manganese, possess the. requisiteproperties to a greater or les'sdegree'.

The choice of a metal from which to make up the chlorsulphonate for our process involvesth'e following considerations: (a) its chloridermust be readily dehydratable and (12') its chloride-must take up S03 readily to form the chlorsulphonate.

We have shown that sodium chlorsulphonate is quitesuitable for our process. Sofar as we know at present, the chlorsulphonates of ammonium, potassium, magnesium, calciumv and other bases are all theoretically possible and suitable toa greater or less degree. As -the properties which render practicable the recycling of the by-prodnets in our process are inherent in the acetate rather than in the chlorsulphonate, we do not wish tobe limited to any particular chlorsulphonate. However, for the reasons. given, we prefer the chlorsulphonates of sodium and vpotassium. I

Although we have used the acetate'for purpose of illustration, we do not wish to be limited thereto, as other unsubstituted carboxylic acids, such as benzoic, caproic, butyric, propionic acids, etc., are within the scope of our invention.

This-application is a continuationin apart .of

':our application SerialNo. 154,631filed ,July 20, l

We claim as our invention:

1. The process for productio'n of anhydrides of unsubstituted monobasic :car-boxylic :acidszfrom the aqueous carboxylic acid which comprises preparing by reaction with said acid a carboxylate of the group consisting of the corresponding carboxylates of barium and zinc, dehydrating said carboxylate and reacting the dehydrated carboxylate with a chlorsulphonate of the group consisting of the inorganic chlorsulphonates which in solution form alkaline cations.

2. The process for production of anhydrides of unsubstituted monobasic carboxylic acids, from the aqueous acid, which comprises reacting the acid with a binary compound, reactive therewith, formed by decomposition of a sulphate of the group consisting of the sulphates of barium and zinc, dehydrating the resulting carboxylate and reacting the dehydrated carboxylate with a chlorsulphonate of the group consisting of the inorganic chlorsulphonates which in solution form alkaline cations.

3. The process for production of anhydrides of unsubstituted monobasic carboxylic acids, from the aqueous carboxylic acid, which comprises reacting said acid with barium oxide, dehydrating the resulting carboxylate and reacting the dehydrated carboxylate with a chlorsulphonate of the group consisting of the inorganic chlorsulphonates which in solution form alkaline cations.

4. The process for production of anhydrides of unsubstituted monobasic carboxylic acids, from the aqueous carboxylic acid, which comprises reacting said acid with barium monosulphide, dehydrating the resulting carboxylate and reacting the dehydrated carboxylate with a chlorsul =phonate of the'group consisting of the inorganic chlors'ulphonates' which in solution form alkaline tion j :iji 121;: 1 i zTheiproces'sifor production j of: anhydridesof unsubstitutedamonobasio 'carboxylic :facids; from the aqueous carboXylic acid which, comprises ,re- "a'ctings'aid acid with-zinc oxide; dehydrating; the resultingxcarboxylategand' reactingthedehydrated ccjarboxylate with a'. "chlorsulphonate jof the, group consisting of the :Linorganic chlorsulphonates which 'in solution formvalkalinee cationsag, j r: 7

4,62 The process for. l production of acetic anhydride from aqueous" acetic" acid. which comprises "reacting said acid withabinary compound, reactivea-tlierewith; formed by decomposition o f a lfsulphatezof the group consisting of the sulphates of .barium' and; zinc; dehydrating, the resulting acetate andreacting the dehydrated acetate with a chlorsulphon'ate of: the group consisting of the iinorganic chlorsulphonates which in; j solution forin'alkalin'e,cationsi :1: a 7.2The1iprocess forfproduction of acetic anhyc :dride'; from aqueous actic acid which-comprises irea'cting i'said acid' with bariumxoxide-r dehydrating the;resulting acetate and reactingthe dehyridrated acetate with? a chlorsulphonate ofthe group consisting *of the inorganic chlorsulph onatesiwhich in solutionform alkaline cations,

- 8. The process for production-of 1 acetic anhydride from aqueous acetic acid-which comprises reacting said acid with barium monosulphide; Idezhydrating the. resulting acetate and reacting .the

'dehydrated': acetate with a chlorsulphonate of the group consisting of the inorganic chlorsul- ,phonates which in solution form alkaline cations.

9. The process forproduction of acetic anhy- Zdride from aqueous acetic acid which comprises reacting said acidwith zinc oxide, dehydrating the resulting acetate and reacting the dehydrated acetate with a chlorsulphonate of the group consisting of the inorganic chlorsulphonates which insol'ution form alkaline cations,

inorganic. chlorides fforming" therewith chlor H phonategwhich in solution form alkaline catipn s and reacting the resulting i:hlorsulphonatev with said dehydrated acetate. 40 l 10 The process for production of acetic-anhy dride from aqueous acetic acid which ,rcomprises reactingsaid acid with barium oxide to produce barium acetate, heating said acetate tofsubstan tially C. and reacting the resultingdehy drated acetate with a chlorsu'lphonate oi 'the group consisting ofthe inorganic, chlorsulpliojnates which insolution form alkaline cations! 11. The process for production of acetic anh dride from aqueous' acetic acid which comprises reacting said acid with bariummonosulphide to produce barium acetate, heating said 'acet'ate to substantially 160 C. and reacting the'resultii'ig dehydrated acetate witha .chlorsulphonate of the groupconsisting of the inorganic chlorsulphdnates which in solution form alkaline cations. T f

, ;12. The process for production offanhyd'ri d s of unsubstituted monobasic carboxyli'c anagram the aqueous carboxylic acid which comprise v actingsaid acid'with barium monosulphide, dehydrating ther esulting carboxylate, oxidizing the resulting hydrogen sulphide to sulphur trioxide, reacting said sulphur-trioxide with an anhydrous chloride of the group consisting of the inorganic chlorides forming therewith chlorsulphonates which in solutionform alkaline cations. and 'reacting the resulting chlorsulphonate with s aidde'ghydratedcarboxylate. 13 The process for production of acetic anhydride from aqueous acetic acidwhich comprises reacting said acid with ,barium sulphida dehyclratingiv the resulting acetate; loicidizing'l'th lt ne hy ea mphesul i sulphur-1 ifoxide, reacting said sulphur'ftri'o'xide :with'anarihydrous chloride or the group'consi'stingf of the j Amman. sunning qJos o iI 

